1. Field of the Invention
This invention relates to a method for manufacturing a tire for vulcanization-molding a green tire.
2. Description of the Related Art
In the manufacture of a tire, a carcass assembly that is a basic component of tire is assembled and molded on an inflated drum in a molding machine of molding step, the tire assembly is taken out from the drum, lateral beads thereof are grasped by a rim, and air is then sealed into the tire to inflate it. Thereafter, a belt member and a tread member are stuck onto the outer surface of the carcass assembly, whereby a green tire is molded.
The green tire is then grasped by the chucking mechanism of a carrying device, carried out from the molding step, and carried to vulcanization step after carried to and temporarily stored in a storehouse on the basis of a production plan, or directly carried from the molding step to the vulcanization step. In the vulcanization step, the green tire placed in a prescribed carrying-in position is grasped by the chucking loader of a vulcanizer, carried to between opened molds, and set so that a bladder is located within the tire hole. Thereafter, the molds are clamped, and a high-temperature, high-pressure gas is supplied into the bladder, whereby the bladder is extended and closely fitted to the tire inner wall surface. The tire inner wall surface is pressed in the mold direction with heating through the bladder, whereby the tire grooves of the molds are formed on the tread of the green tire, and the resulting green tire is vulcanized by heating from the outside and inside by the heated molds and the bladder exposed to the high-temperature pressure gas.
However, in the above-mentioned conventional method, even if the green tire is precisely formed in the molding machine, the rubber-made green tire is apt to deform in the course of carrying since it is grasped by the chucking mechanism to take and place it in the carrying-in position of the storehouse or vulcanization step, and then re-grasped again to carry it into the vulcanizer. Therefore, when the green tire is carried into the vulcanizer, the supporting center of the green tire is significantly slipped, which brings about the problem that the precision of vulcanization molding is apt to deteriorate.
It is therefore an object of this invention to provide a method for manufacturing a tire capable of significantly reducing the slippage of supporting center of the green tire in the carrying to the vulcanizer.
The method of this invention comprises molding a green tire in molding step and carrying it into the mold of a vulcanizer in vulcanization step to vulcanization-mold the green tire, in which the upper bead and lower bead of the green tire are connected and fixed as they are kept in the airtight state until the molded green tire has been carried into the mold of the vulcanizer, and a pressure gas is sealed to the internal space of the green tire to lay it in the expanded state. According to the above constitution, since the green tire is carried between the respective steps and carried into the mold in the state maintaining a fixed shape, the deformation in carrying of the green tire can be prevented. Thus, when the green tire is set in the vulcanizer, the slippage of supporting center of the green tire can be sufficiently reduced.
The method of this invention comprises molding a green tire on a bladder in molding step and carrying it into the mold of a vulcanizer in vulcanization step to vulcanization-mold the green tire, in which the upper bead and lower bead of the green tire are connected and fixed as they are kept in the airtight state until the molded green tire has been carried into the mold of the vulcanizer, and a pressure gas is sealed to the bladder located in the internal space of the green tire to lay it in the expanded state. According to the above constitution, since the green tire is carried between the respective steps and carried into the mold in the state maintaining a fixed shape, the deformation of the green tire can be prevented. Thus, when the green tire is set in the vulcanizer, the slippage of supporting center of the green tire can be sufficiently reduced.
In the above-described method, the bladder has a low drawable material difficult to deteriorate under high-temperature environment as the component, and it is formed into the shape of the tire inner wall surface in the vulcanized tire obtained by vulcanization molding the green tire. According to this constitution, the green tire can be precisely formed and also vulcanization-molded. The bladder may have a plurality of magnetic members on the surface. According to this, since the magnetic members can be directly heated by use of an induction heating coil, the temperature can be raised to the vulcanization temperature in a short time.
The above-mentioned method is further characterized by performing the vulcanization molding in the vulcanizer while maintaining the connection and fixation between the upper bead and lower bead of the green tire. Since the connection and fixation between the upper bead and lower bead is maintained when the high-temperature, high-pressure pressure gas is supplied to the internal space of the green tire to press the tire inner wall surface in the mold direction, the opening of the mold can be surely prevented even if the clamping force to the mold is small. According to this, the frame structure of the vulcanizer for imparting the clamping force to the mold can be set to a specification corresponding to a small clamping force, and the vulcanizer can be consequently miniaturized to reduce the cost.
The method of this invention comprises arranging a retaining mechanism in a tire molding machine in molding step; molding a green tire around the retaining mechanism; connecting and fixing the upper bead and lower bead of the green tire while keeping them in the airtight state; sealing a pressure gas to the internal space of the green tire to expand it prior to the taking-out from the molding step; carrying the green tire to vulcanization step in this state; and vulcanization-molding the green tire within the mold of a vulcanizer in the vulcanization step. Further, this method comprises arranging a retaining mechanism and a bladder in a tire molding machine in molding step; molding a green tire on the bladder; keeping the bladder in the airtight state; sealing a pressure gas to the bladder located in the internal space of the green tire to expand it prior to the taking-out of the green tire from the molding step; carrying the green tire to vulcanization step in this state; and vulcanization-molding the green tire within the mold of a vulcanizer in the vulcanization step. According to this, since the green tire is carried between the respective steps and carried into the mold in the state maintaining a fixed shape, the deformation in carrying of the green tire can be prevented. Thus, when the green tire is set in the vulcanizer, the slippage of supporting center of the green tire can be sufficiently reduced.
In the above method, the bladder has a low drawable material difficult to deteriorate under high-temperature environment as the component, and it is formed into the shape of the tire inner wall surface in the vulcanized tire obtained by vulcanization molding the green tire. The bladder may have a plurality of magnetic members on the surface. Further, the retaining mechanism may have an induction heating coil, so that the vulcanization molding is performed with addition of a high frequency power in the vulcanization molding by the vulcanizer. Since the magnetic members can be directly heated by use of the induction heating coil, the temperature can be raised to the vulcanization temperature in a short time.
In the above method, the retaining mechanism may be provided with an upper bladder ring and a lower bladder ring to seal the pressure gas after the upper edge and lower edge of the bladder are held by both the rings. In the method according to claim 8, the green tire may be carried into storage step prior to the carrying into the vulcanization step, preheated during the storage, and then carried to the vulcanization step.